Data import fails

Data import seems to be failing according to https://gitlab.com/sunpeek/support/-/issues/16#note_2792947085

Steps to reprocude:

1. install the newest SunPeek installation using https://docs.sunpeek.org/
2. click on "install "try the demo" to create a demo plant
3. At the demo plant - go to arrays - go to edit array - and go to the collector selection screen.
4. Next, Edit the collector so it works with a K50 for the IAM instead of the IAM_Method (from 0°-90°). Save everything.
5. Go back to the plant-selection, click on export
6. Use the exported file, and try to import it again -> An Error appears!

The cause of the error seems to be that the value "b" is included in the json file, but the backend does not know what to do with it.

"iam_method":{"method_type":"IAM_K50","k50":{"magnitude":0.97,"units":""},"b":{"magnitude":0.0539836489817009,"units":""}}

By removing the b it is functional again:

"iam_method":{"method_type":"IAM_K50","k50":{"magnitude":0.97,"units":""}}

cc @p.ohnewein @lbonal